1. Field of the Invention
The present invention relates to a thin film magnetic head in which the amount of flying is controlled by locally protruding an element portion toward a recording medium side through thermal expansion.
2. Description of the Related Art
A thin film magnetic head is provided with at least one playback element, which includes a multilayer film exhibiting a magnetoresistance effect between a lower shield layer and an upper shield layer and which reads magnetic information from a recording medium on the basis of the change in resistance of the multilayer film. The thin film magnetic head also includes a recording element which includes a pair of magnetic core layers opposed to each other with a magnetic gap layer therebetween on a medium-facing surface and which gives a recording magnetic field leaking from the magnetic gap layer to the recording medium so as to record the magnetic information. In a so-called compound type thin film magnetic head provided with both the playback element and the recording element, the recording element is laminated on the playback element.
In the thin film magnetic head, it is desirable that the spacing between the element portion including at least one of the playback element and the recording element and the recording medium opposed to each other is controlled to become small in order to improve the head characteristics (playback characteristics, recording characteristics). Heretofore, various thin film magnetic heads have been proposed, in which element portions are allowed to protrude toward the recording medium side by on the order of a few nanometers through thermal expansion by using heating elements which generate heat during energization. The heating element is formed with a flat pattern parallel to film surfaces of individual layers constituting the thin film magnetic head, and is disposed between any two layers. Specifically, the heating element is disposed as a layer under a lower core layer, as a layer on an upper core layer, between the lower core layer and the upper core layer, in a surface protective layer, or the like. The thin film magnetic heads provided with the above-described heating elements are described in US 2004017638 A1, Japanese Unexamined Patent Application Publication No. 2005-11413, and the like.
However, when the element portion is intended to protrude toward the recording medium side, the periphery of the element portion is also thermally expanded and, therefore, it is difficult to control in such a way that the protrusion of the element portion becomes the largest. In the case where the amount of protrusion of the periphery of the element portion is larger than that of the element portion, the periphery of the element portion is brought into contact with the recording medium prior to the contact of the element portion, and, thereby, not only the recording and playback characteristics may deteriorate, but also the recording medium may be damaged. In order to reduce the amount of protrusion of the periphery of the element portion, a heat dissipation plate may be disposed for releasing the heat of the periphery of the element portion to the outside. However, it has not yet been realized because, for example, the process becomes complicated, or a layer for formation of the heat dissipation plate is restricted.
Furthermore, there is a problem in that a local temperature increase occurs in the electrode lead used for energizing the heating element. The electrode lead of the heating element is usually disposed in an alumina insulating layer, most of the electrode lead has a width larger than the line width of the heating element in order to reduce the electric resistance, and a narrow connection wiring portion connecting between the wide wiring portion and the rear end of the heating element in the height direction is included. Since the electric resistance of the connection wiring portion is larger than that of the wide wiring portion, when a current passes through the electrode lead, local heat generation occurs. A local temperature increase in the electrode lead may cause a break due to migration and, thereby, the reliability deteriorates.